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When a Mars rover leaves a trail of tracks in the Martian dunes, is it a tragic imprint of human intrusion on a pristine alien landscape billions of years old, or the first hopeful sign of intelligent life arriving on a long-dead planet? Such an extraterrestrial scenario could help humans consider the moral consequences of shaping environments on Earth. The Mars rover scenario represents a stark illustration of a debate that has raged in the environmental community for decades — whether to keep environments completely free of the contamination from human influence or whether to take the pragmatic approach of regulating how humans change their environments. Over the past year, David Grinspoon, the first NASA/ Library of Congress Astrobiology chair, has tried to connect the dots between astrobiology's study of life in the universe and how humans deal with environmental issues on Earth.

Many human activities, notably usage of fossil fuels to power modern civilization, have contributed to the rise in carbon dioxide. Humans have a responsibility for their actions because they possess the consciousness and intelligence to look into the future and anticipate some consequences. A technological breakthrough or "game changer" could help humans continue to produce the energy they need without impacting the Earth's environments and climate even more, Grinspoon suggested. "We have to learn to become a new kind of entity on this world that has the maturity and the awareness to handle being a global species with the power to change our planet and use that power in a way that is conducive to the kind of global society we want to have," Grinspoon said. Science fiction has often imagined a fantasy of intelligent aliens coming to tell humans how to handle matters on Earth.

But without an ET intervention, humans will have to look to literature, history and science to figure out how to keep their advanced civilizations going sustainably far into the future.